"For a 64-bit integer, you have no other choice than to perform the division, …"

And 64 bit systems become more and more common. Espacially in the Unix sector.

size_t will become 64 bit there, and in the open source community you have to make the checks bulletproof on every architecture because the code is often widely used… from x86_32, over 31 bit s390, to ppc64.